1. Field of the Invention
The present invention relates to a paper machine, and, more particularly, to a method and apparatus for removing water from a fibrous web using a dewatering fabric and a permeable press belt in a paper machine that reduces or eliminates mechanical pressing thus increasing sheet quality.
2. Description of the Related Art
The Voith Paper patented TissueFlex process substitutes a shoe press for the conventional suction pressure roll in a typical Tissue paper machine. The shoe press provides a wider nip that lowers peak pressure, which has shown an increase in sheet caliper and absorbency. These gains are in the 10% to 20% range depending on furnish and overall load. The suction pressure roll is relocated to a position prior to the nip to dewater the press fabric and sheet prior to reaching the shoe press as disclosed in U.S. Pat. No. 6,235,160.
The sheet solids going into the shoe press when running a conventional press fabric on a Crescent former fitted with the TissueFlex process is about 23%. Post shoe press solids are in the 37% to 41% range depending on furnish and overall load.
A fabric is utilized to carry the fiber web during the formation of the web. After the web takes form it is usually subjected to a drying process. The same fabric used during formation of the web or another fabric may come in contact with the web, to move the web across a vacuum section for the remove of moisture from the web. The fabric may additionally absorb moisture from the web and the moisture so absorbed is subsequently removed from the fabric at a later point in the process.
A problem with conventional fabrics is that they carry too much water and rewetting is one of the major issues relative to light basis weight papers, such as tissue. Further, independent of the vacuum applied the sheet solids remain in the 23% to 25% range.
What is needed in the art is a more efficient method of removing water from a fibrous web.